Code to get an Amazon Echo isn't working

Hello,

In July I published a Skill during a promotion.

A month ago I received a code to get an Amazon Echo dot, which worked and I received the echo dot a few days after.

This skill was downloaded more than 200 times and yesterday I received a code to get an Amazon Echo for free. This code isn't working though..The Amazon.com and Amazon.fr support won't be able to help me